This is a really basic one. I took the offensive stats for each team through July 20th (the last time I got the totals into Excel) and took each pitchers' performance through July 26th. I took the top 115 starting pitcher in innings pitched and tossed in Clemens just for fun. I used each pitcher's actual runs given up per game (era but using runs instead of earned runs) and each teams' actual offensive performance so obviously a team or pitcher that varies from that average will vary from the listed winning percentage the rest of the way. I also did not factor in strength of schedule, bullpen support or any other factors that could affect winning percentage for pitchers. This is just a quick and dirty look at which pitchers are most likely to post the most wins the rest of the way.
You can read the full results here but here are the top 20 pitchers in expected winning percentage along with that percentage:
I think the names that really jumps out at me off that list are Johnson (.652) and Wang (.631). All the other guys are valued fairly highly by people. Johnson and Wang could be very good plays for wins down the stretch though and they might come cheaper than some other options off the list. Johnson I seriously question as he may not keep up his great pitching (the only reason he made the list with the Marlins backing him up). Wang on the other hand has the Yankees offense behind him...not a bad way to get a few wins.